Interpretive Summary: To clone and characterize dormancy genes in cereal crops, a weedy rice strain 'SS18-2' was selected as the gene donor. Tissue component analysis using a "somatic" approach for dormant seeds from parent and selected F2 plants demonstrated that dormancy is controlled by the maternal genotype. Genetic analysis based on the germination at 30 C and 100% RH at 0, 20, 40, and 60 days after harvest (DAH) revealed that the broad sense heritabilities for the seed covering-imposed dormancy were 71, 94, 90, and 87%, respectively, in the mapping population. Similar bimodal distributions occurred at 20 DAH in the reciprocal F2 populations suggesting at least three genes are responsible for dormancy. These results were verified by germinating the seeds from one ratooning F2 population in the next season (r ranging from 0.5** to 0.7**). Polymorphism between parents at the molecular level is 70%. A bulked sergeant analysis approach and microsatellite markers are been using to mark the location of major genes. To diminish the influence of genetic background on phenotyping, F2 plant-derived backcross (BC) populations have been advanced to BC2F1 generation. A more distinct bimodal distribution detected in the BC1F1 population with regard to the germination at 20 DAH verified the presence of major genes. Linked markers will be used to delimit the target chromosomal regions, to select nearly isogenic lines, and to select recombinants to construct high-resolution maps in the target regions.

Technical Abstract:
To clone and characterize dormancy genes in cereal crops, a weedy rice strain 'SS18-2' was selected as the gene donor. Tissue component analysis using a "somatic" approach for dormant seeds from parent and selected F2 plants demonstrated that dormancy is controlled by the maternal genotype. Genetic analysis based on the germination at 30 C and 100% RH at 0, 20, 40, and 60 days after harvest (DAH) revealed that the broad sense heritabilities for the seed covering-imposed dormancy were 71, 94, 90, and 87%, respectively, in the mapping population. Similar bimodal distributions occurred at 20 DAH in the reciprocal F2 populations suggesting at least three genes are responsible for dormancy. These results were verified by germinating the seeds from one ratooning F2 population in the next season (r ranging from 0.5** to 0.7**). Polymorphism between parents at the molecular level is 70%. A bulked sergeant analysis approach and microsatellite markers are been using to mark the location of major genes. To diminish the influence of genetic background on phenotyping, F2 plant-derived backcross (BC) populations have been advanced to BC2F1 generation. A more distinct bimodal distribution detected in the BC1F1 population with regard to the germination at 20 DAH verified the presence of major genes. Linked markers will be used to delimit the target chromosomal regions, to select nearly isogenic lines, and to select recombinants to construct high-resolution maps in the target regions.